If the world wants an image that sums up the true cost of supplying big-name retailers with cheap, fast fashion, it only has to ponder the horrifying images coming out of Dhaka as thousands of frantic relatives and rescue workers continue to claw through the rubble of Bangladesh’s worst industrial disaster in a desperate search for survivors. Many people remain trapped in the remnants of the multistory Rana Plaza — home to several garment factories — after the building collapsed in the Bangladeshi capital on Wednesday, killing over 300, according to the latest figures, and injuring more than 1,200. Bangladesh’s government declared an official day of mourning on Thursday and the death toll is expected to climb as more bodies are found.

The first three floors of the building, located in the Dhaka suburb of Savar, contained around 300 shops. At least four garment factories — New Wave Bottoms, Phantom Apparels, Phantom Tack and Ethar Textile — occupied higher levels, employing around 3,500 people. On its website, New Wave claims to supply major Western retailers from the U.S. and Europe. Ethar claims to produce clothes for Walmart, but this has been challenged by the U.S. giant. Other firms have also distanced themselves from the disaster. Only Britain’s Primark freely admitted that it was using a factory in Rana Plaza. What is not in dispute, however, is the cruel reality of the global rag trade: in order for consumers in developed economies to enjoy tasteful clothes at affordable prices, low-paid workers in countries like Bangladesh must toil in dangerous, sometimes lethal, conditions.

Officials say the building showed cracks on Tuesday, but the owner, Sohel Rana, a local leader of the ruling Awami League party’s youth wing, allegedly dismissed them as “nothing serious.” Activists claim the tragedy could have been avoided had staff in Rana Plaza been unionized and thus in a position to defy the order to ignore the danger. “The managers forced us to return to work, and just one hour after we entered the factory the building collapsed with a huge noise,” one survivor tells TIME. She was desperately trying to find her husband who had been working on the fourth floor.

Brad Adams, Asia director at Human Rights Watch, said in a statement on the organization’s website that the Rana Plaza tragedy was predictable given the long record of worker deaths in factories in Bangladesh. “The government, local factory owners and the international garment industry pay workers among the world’s lowest wages, but didn’t have the decency to ensure safe conditions for the people who put clothes on the backs of people all over the world.”

Accusations are circulating that the building was constructed on marshy land that violated planning regulations, and had been constructed with eight floors despite only having permission for six. But enforcement is lax. Although the law allows for those responsible for violating workplace health-and-safety provisions to be jailed, infractions more commonly result in paltry fines.

Around 4 million people are employed in Bangladesh’s 4,500 textile factories. The industry generates 80% of the country’s $24 billion annual exports — making Bangladesh the world’s second largest clothing exporter after China — yet wages remain as low as $37 per month for workers spending 15-hour shifts in sweatshop conditions. Building collapses are unsettlingly common, especially in the overcrowded capital where construction laws are frequently ignored. An estimated 500 people have been killed in similar disasters over the past decade, including 73 garment workers in a similar factory collapse in Savar in April 2005.

Rana Plaza has also brought back painful memories of the fire at Tazreen garment factory at Ashulia, another suburb of Dhaka, in November that claimed the lives of 112 people. The failure to follow safety regulations was once again at the heart of that tragedy (fire escapes were bolted shut) and fierce protests erupted in its aftermath. Retailers such as Walmart, Gap and Disney were lobbied to ensure their products were sourced responsibly from workplaces that adhered to decent standards of worker rights and safety.

Pressure is again mounting for some action to be taken in the wake of the Rana Plaza collapse. Bangladesh is a beneficiary of the U.S. Generalized System of Preferences (GSP), which promotes economic growth in developing nations by allowing duty-free imports. However, for many years advocacy groups have asked for Bangladesh’s GSP status to be revoked over concerns regarding poor working conditions. Dan Mozena, U.S. ambassador to Bangladesh, who has previously argued for maintaining GSP in the South Asian nation, admitted on Thursday that this latest disaster would impact the ongoing debate. “It’s a horrible day, and it’s a sad day, and I am deeply sorry,” he said.

Many garment workshops in Dhaka and its suburbs suspended operations on Thursday amid angry protests. Furious workers armed with crude weapons blocked highways and broke windows in several factories. The owner of Rana Plaza, along with the managing directors and chairmen of garment factories housed within the building, has been summoned to appear at Bangladesh’s High Court by April 30, and the government has been petitioned to launch a judicial inquiry. The world’s shoppers won’t be receiving a summons, of course, but there is no denying that we, and the retailers we buy from, all share a moral responsibility in the tragedy at Rana Plaza.